The use of a velocity profile to control the motion of an elevator car is well known. See, for instance, U.S. Pat. No. 4,751,984 entitled "Dynamically Generated Adaptive Elevator Velocity Profile", as well as pending U.S. patent application Ser. No. 07/375,429 entitled "Elevator Speed Dictation System", both of which are owned by the Assignee hereof and both of which disclose how to generate velocity or motion profiles for an elevator car.
Motion control of an elevator car involves regulating the movement of an elevator car from an origin floor to a destination floor. Car motion may be controlled by using jerk rates, acceleration rates and deceleration rates to regulate the rate of change of acceleration and velocity to maintain the forces acting on a passenger within the car within a subjective comfort zone. A typical motion profile also includes a maximum desired speed which the elevator car will attain during longer floor runs, also known as the contract speed. A feedback loop is often used to regulate the car motion throughout the run and particularly as the car decelerates to a stop as it approaches the destination floor.
Designers of elevator systems have typically preselected a motion profile for each elevator system. This motion profile represents a compromise between fast flight times and increased capacity as opposed to slow flight times and increased comfort. The profile selected for each elevator might vary depending upon the particular market where the elevator would be installed and the expectations of customers on a desired comfort level and the need for faster service. For instance, Far Eastern passengers prefer a motion profile with relatively slow jerk and acceleration rates such that a smoother, more comfortable ride is obtained and are more willing to wait longer for the elevator car to arrive than other passengers. The typical North American passenger is less concerned with comfort and is more concerned with fast flight times and decreased waiting time and, therefore, would prefer to have the elevator car operated at a faster profile with slightly less passenger comfort due to the higher acceleration and jerk rates.
In the past the motion profile selected to operate the elevator car did not vary dependent upon whether or not passengers were in the car. Hence, the motion profile selected would have appropriate jerk and acceleration rates for a smooth passenger ride even if no passengers were in the car and, consequently, the elevator car would take longer to get from the origin floor to the destination floor than it would if it were immediately operated at the highest available acceleration and jerk rates to accelerate to contract speed. Hence, it is possible to increase overall elevator system capacity and to reduce the average waiting time of the passenger for an elevator car by operating the elevator car when there are no passengers in the elevator car at a faster motion profile resulting in a reduced flight time.
The selection of a motion profile may be based on various means of determining whether or not a passenger is present in the elevator car. Loadweighing may be utilized to sense the load in the car. Also, whether or not any car calls have been entered by pressing the buttons in the car operating panel within the elevator car is also indicative of whether or not passengers are present. Furthermore, whether or not passengers are present is only a determination which may be delayed until after the elevator car is committed to move to another floor to pick up passengers. During those periods when it is determined that the elevator car is empty, a faster motion profile (motion profile with a higher acceleration, jerk and deceleration rates) is used to reduce the flight time between the floors. During periods when a passenger is detected in the elevator, a slower motion profile (motion profile with lower acceleration, jerk and deceleration rates) is selected which provides the desired elevator performance while maintaining a comfortable ride. As used herein, the flight time is that time period extending from the closing of the elevator doors at the origin floor until the opening of the elevator doors at the destination floor.
Overall elevator system performance may be improved by operating the elevator car under a motion profile which maintains passenger comfort when passengers are present and by operating the elevator car under a high performance profile with higher acceleration and jerk rates to reduce elevator flight time when there are no passengers in the elevator car.